Disclosed herein arc multispectral detection methods and systems that can be used with image-forming optics configured to form an image of a sample. The systems include: (a) an imaging detector; (b) relay optics that include multiple optical elements, the relay optics positioned to relay the image formed by the image-forming optics to the imaging detector; (c) an actuator coupled to one of the optical elements in the relay optics and configured to adjust a position of the coupled optical element; and (d) control electronics configured to cause the actuator to adjust the position of the coupled optical element in the relay optics in response to a wavelength band selection by a wavelength selection element positioned to select one wavelength band for the image from among two or more wavelength bands within an overall wavelength range.